Ouch. Evan Bourne's an incredibly entertaining wrestler, and he's someone that I'm sure we'll be seeing a lot of for the next few years, but he's simply out of his league right now in a match like this - especially in WWE territory.
The Rock has a height advantage, a strength advantage, the experience, the credentials...pretty much everything over Bourne, except for versatility and speed. However, The Rock isn't a lumbering slow guy like Big Daddy V, so the speed thing isn't that much of a factor in the long run, and while Bourne may be able to think of odd counters and stuff, that won't be enough to pull out a win here.
Bourne gets a couple of really good shots in there, but in the end, will wind up getting caught mid-air, followed by a Rock Bottom and the 3-count. Three years from now, it'll be interesting to see how perspectives may change, but right now, The Rock has this down with no doubt whatsoever.